The widespread harvesting of timber has increased the need for improved re-forestation practices. Most re-forestation planting is done in areas previously logged. It is common for re-forestation planting to be accomplished by manual labor, but such an approach is costly. The high cost of manual planting is caused by the difficulty of the work, the large amounts of area which must be covered, and the large volume of tree seedlings which must be planted. There have been numerous attemps to design a suitable tree seedling planter which is effective and efficient. To date all mechanized tree seedling planters have suffered from one or more limitations which have deterred acceptance of these implements by the lumber industry.
Of particular significance to this invention are problems experienced in prior art seedling holders and dispensers. The seedling holder is subjected to severe service since it must hold the seedling and appropriately release the seedling as it is placed into the ground. Correct placement of the seedling within the soil layer is one of the most important factors in seedling survival. The seedling must be properly held and appropriately released to achieve acceptable position and orientation within the ground.
The insertion and removal of mechanized seedling holders has previously caused substantial maintenance and operational problems. The seedling holder operates in the soil under conditions of moisture and a variety of soil compositions. Some soils are highly abrasive, while others are gummy and sticky. Nearly all are likely to contain sufficient amounts of organic matter or other constituents which can cause fouling or plugging.
Prior art seedling holders have typically functioned to eject a seedling by using a linear ejection mechanism. Such mechanisms often entail bulky and relatively heavy mechanisms. Use of such heavy mechanisms on a movable planting arm can significantly reduce the speed of operation because of the larger mass which must be repeatedly accelerated and decelerated during cycling of the planting arm. Accordingly there is a need for minimizing the mass and inertia associated with a seedling holding and planting apparatus.
Another deficiency of the prior art is the efficient and automatic operation of the seedling holder into open positions at both the loading and unloading positions. Prior art seedling holders such as shown in U.S. Pat. No. 3,899,985 to Rath are only capable of manual loading, thus requiring manipulation of an operator handle to load a seedling into the seedling holder. Although the Rath patent shows release of the seedling holder in the extended position, the absence of automatic opening in the retracted loading position creates a very significant amount of delay and greatly reduces the rate of speed at which seedlings can be planted.
Until the present invention there has remained a strong need in the art for an efficient, reliable, and automatic seedling holder and dispensing mechanism for use in planting seedlings, particularly tree seedlings.